Binder composition for preparing fiber mats

ABSTRACT

A mixture for producing moulded articles from fibre mats containing 
     a) 20 to 45 wt. % of a powdered binder mixture, 
     b) 80 to 55 w. % of organic and/or inorganic fibres, 
     characterised in that the powdered binder mixture contains 
     a1) 30 to 90 wt. % of phenol resin and 
     a2) 70 to 10 wt. % of powder coating waste 
     and moulded articles produced therefrom.

This application is a 371 of PCT/EP95/01643 filed Apr. 29, 1995.

FIELD OF THE INVENTION

The invention relates to a special binder composition for preparingfibre mats and a method for its preparation. The prepregs produced fromthe fibre mats and binders are also described.

BACKGROUND OF THE INVENTION

Moulded articles based on fibre mats are used extensively in industry.These consist of a matting made of fibres of various kinds which can bemixed with binder. Intermediates can then be produced from these fibremats, so-called prepregs, which are then moulded with the appropriateprocessing mould, cured and optionally backed. Likewise, it is alsopossible to prepare corresponding continuous fibre mats directly fromthe fibres and binder powders. These moulded articles or sheet productsare used in a wide range of areas. In the automobile industry, forexample, these products are used as moulded articles, e.g. as insulatingmaterial for engine bonnets, as wheel arches or as boot insulation.Another field of use is application as sheet products, e.g. asinsulation in washing machines, tumble-driers or loud speakers, insound-absorbing walls. They may also be provided with further coatings,e.g. by flock spraying, backing or laminating. These moulded articles orsheet parts thus provided with an optically stable and decorativesurface coating can then be used e.g. as door side panels, as rearparcel shelves or as roof panels in the automobile industry.

The methods for preparing fibre mats and for mixing these mats withbinder powder are known. In these, the fibrous material is homogenised,e.g. in a fibre mixing chamber, and laid out as a loose fibrous layer ona conveyer belt.

The binder mixture is then applied to the fibrous material, e.g. withfeed rolls or vibrating chutes. Then the fibre/binder mixture is swirledusing a current of air in a sealed system and homogenously mixed. Thehomogeneous mixture of fibres and binder powder is laid out to give acontinuous mat. The components in this mixture may then either be stucktogether by slightly warming and then cooling, wherein prepregs areproduced, or produced as sheet or rolled up products which are alreadyfully cured. The prepregs are not finally cured but they arestorage-stable. After processing in the final mould, these prepregs arethermally cross-linked under the effects of heat, at up to 210° C.,wherein three-dimensional thermoset moulded articles are obtained.

The demands placed on these moulded articles with respect to surfacestructure and colour are variable, but adequate mechanical stabilitymust be provided at elevated temperature or under long-term stress. Abinder must be used when preparing them, however, which binds togetherthe fibre mats used so well that a stable moulded article is obtainedafter the final moulding and curing procedures. The binders currentlyused are relatively expensive. In addition, phenol resins are hazardousto health. The industry is extremely interested in reducing the costs.Alternatives to the expensive, technically pure resins are being soughtin particular for the moulded articles described above such asinsulating materials for car bonnets, for wheel arches and for otherinsulating materials.

SUMMARY OF THE INVENTION

The present invention provides a binder mixture for producing fibrematting moulded articles in which a considerable part of theconventionally used pure resins can be replaced by another componentwhich nevertheless leads to stable, reactive binder mixtures which aresuitable for producing fibre matting prepregs or cured fibre mats. Theinvention also provides a reduction in the proportion of substanceshazardous to health. These binder mixtures have to satisfy theconventional requirements for the production of fibre matting mouldedarticles and thus produce cured, stable moulded articles which can beadapted to a wide variety of applications.

It has been shown that this object can be achieved by the use of powdercoating waste as or in binders for producing moulded articles from fibremats. Surprisingly, it was found in fact that conventionally used resinscan be replaced to at least a considerable extent by powder coatingwaste.

One object of the invention is a mixture for producing moulded articlesfrom fibre mats, containing

a) 20 to 45 wt. % of a powdered binder mixture,

b) 80 to 55 wt. % of organic and/or inorganic fibres, which ischaracterised in that the powdered binder mixture contains

a1) 30 to 90 wt. % of phenol resin and

a2) 70 to 10 wt. % of powder coating waste.

A further object of the present invention is use of the powder coatingwaste to produce moulded articles which contain fibre mats.

A further object of the invention is use of this lacquer waste to bondfibre mats.

DETAILED DESCRIPTION OF THE INVENTION

Powder coatings are being-used to an increasing extent in the lacquerindustry. This has the advantage that a solvent-free application processcan be used. Emissions to the environment can thus be greatly reduced.The application methods for powder coatings, however, have thedisadvantage that a considerable proportion of the powder does not reachthe object being coated. This powder is collected in the lacqueringcubicles as so-called overspray. Powders are sensitive with regard todistribution of particle size and purity. Therefore this overspray hasto be disposed of as waste. In the last stage of powder coatingproduction, the crushed powder coating extrudates are milled. Fine dustis produced during this milling process which can interfere with thelacquering process. Therefore, this dust is largely removed. This dustis very difficult to reprocess and has to be disposed of as specialwaste.

The fibres which can be used for the various fibre mats are woven,felted or blended fibres. The fibres consist of known materials, e.g.natural, organic and inorganic fibres. Examples of these are glassfibres, mineral wool fibres, polyester fibres, acrylic resin fibres,polyolefin fibres, wool fibres, cotton fibres, flax fibres or the like.Textile fibres, in particular cotton fibres, e.g. fibre waste from thetextile industry, are preferably used. These fibres or the fibre matstherefrom are known in industry. Also known are the processes by whichthey may be produced. This takes place, for example, by weaving orfelting. The fibre mats produced should be essentially dry, they mayoptionally be impregnated with additives.

The phenol resins which can be used in the mixtures according to theinvention are conventional reactive phenol resins which have been knownin the industry for a long time. Examples are reactive,non-cross-linked, OH groups containing powdered resins. Such resins werealready used for the preparation of prepregs from fibre mats. As anexample, phenol resins based on phenol and formaldehyde such as areknown, for example, as resols or novolaks, may be used. These resins maycontain condensation products of formaldehyde as possible cross-linkingagents.

These resins have already been extensively described in the literature,e.g. in R. N. Shreve, "The Chemical Process Industries", Chapt.Plastics, 1945 and are commercially available. Further phenol resins arealso described in DE-A-38 33 656, EP-A-0 369 539 and EP-A-0 376 432.Phenol resins of the novolak type are particularly preferred.

The reactivity of phenol resins is determined by the type and amount ofcross-linking agent used. In general a cross-linking reaction occurs atbetween 120° and 222° C.

The resins are generally present as powders. Suitable particle sizes arefor example, between 0.1 and 500 μm, preferably between 2 and 150 μm, inparticular between 10 and 60 μm.

The particle sizes of the powder coating waste are, for example, in thesame range as that of the resins and are preferably between 1 and 300μm, in particular between 10 and 60 μm. If powder coating waste is usedwhere the particle sizes are too small for the desired application, itis possible to obtain larger particle sizes by caking the particles.

The powder coating wastes which can be used according to the inventionare those from conventional, known powder coatings. The binders in thepowder coatings may be, for example, based on epoxide resins, polyesterresins, polyurethane resins or acrylate resins. These powder coatingwastes are produced for example, as overspray from lacquering cubiclesor as reject batches during the production of powder coatings.Furthermore, it is possible to collect and use filter dusts as well asresidues from the milling of powders.

The powder coating wastes which can be used in the mixture according tothe invention are not cross-linked. They contain reactive groups suchas, for example, carboxyl groups, epoxide groups, hydroxyl groups, aminogroups, amide groups or isocyanate derivatives. These can react witheach other when heated. The cross-linking temperature depends on theirstructure. Generally it is between 120° and 220° C. Powder coatings withcross-linking temperatures higher than 180° C. are preferably used inonly small amounts in order to achieve the fullest possible extent ofcross-linking for the binder mixture used at curing temperatures for themoulded articles of about 160° C. In addition, at elevated cross-linkingtemperatures, in particular when using fibre mats made from plasticsfibres, there is a risk that the fibres may be degraded, which leads toa decrease in the stability of the moulded article. The powdercoating/cross-linking temperatures are preferably below 160° C.

The powder coatings used are known binder systems. They are conventionalresins based on, for example, epoxides, polyesters, polyurethanes oracrylates.

Epoxide powder coatings contain epoxide resins as the main bindercomponent. These frequently cross-link via hardeners which containhydroxyl groups, in particular amide or amine groups.

Furthermore, polyester powder coatings are known, in which the mainbinder constituents are carboxyl-containing polyesters. Proportions ofcross-linking agents which are present are, for example, cross-linkingagents which contain epoxide groups or cross-linking agents whichcontain amino or amide groups. In this case it is conventional that eachcross-linking agent has more functions than the main binder component.If epoxide/polyester mixed powders are used, so-called hybrid systems,then approximately equal amounts of polyesters and epoxide resins arepresent.

Polyurethane powder coatings are based on hydroxyl-containing polyesterswhich can be cross-linked via reversibly blocked polyisocyanates whichcan be protected with, for instance, known capping agents such ascaprolactam or ketoxime, or are present as the uretdione.

Coating powders of the acrylate type are in general mixtures of two ormore acrylate resins, each of which contains functional groups such asepoxide groups, carboxyl groups, hydroxyl groups or isocyanate groups.Here, the groups which can react with each other are distributed ondifferent molecules.

These binder powders are described in, for example, S. T. Harris, "TheTechnology of Powder Coatings", 1976 or in D. A. Bate, "The Science ofPowder Coatings" vol. I, 1990.

Colourless or pigmented powder coatings may be used, whereinconventional, known, inorganic or organic coloured pigments may be usedas pigments. It is also possible to incorporate special effect pigments,e.g. metal pigments, in the powders. Separation by shade of colour isnot required. The degree of fineness of the powder is not an essentialfactor, care should be taken only that in general an average sample ofthe different powder residues is used for producing the binder mixture.This leads to better mixing behaviour and to a more uniform productionof binder mixture.

Any individual powder coatings may be used. In order to achieve asconstant as possible a composition for binder mixture a), a mixture ofepoxide powders and polyester powders is preferably present as a2).Here, up to 60 wt. %, preferably up to 30 wt. %, of a2) may optionallybe replaced by polyurethane powder and/or polyacrylate powder. In thiscase it is possible to prepare directly a mixture a2) within the desiredratios by weight and to store it in this form. Another possible mode ofworking is to store the different powder coating components of thechemical types described above separately and only later to mix thesewith the phenol resins prior to further processing. Within thesechemical types, the materials produced are mixed homogenously, i.e.thoroughly mixed samples are produced with regard to distribution ofparticle sizes, composition and pigmentation. The powder coating bindersproduced from the mixtures present in this form are then mixed in therelevant amounts required for preparing binder powder a). Optionally, itis possible to incorporate further additional cross-linking agents inthe binder mixture.

The powder coating wastes which can be used according to the inventionare present as millable powders. Optionally, it may be required to milla proportion of the binder which is present in a relatively coarse formto a suitable particle size beforehand. This size may be of the order ofmagnitude given for the phenol resins.

Conventional additives or auxiliary agents may optionally be addedtogether with the powders. These may be, for example, catalysts,accelerators or flame retardant agents. The catalysts used arepreferably tin compounds such as dibutyltin dilaurate, carboxylate saltssuch as lithium benzoate, quaternary ammonium compounds such astetrabutylammonium bromide, cetyltrimethylammonium bromide,benzyltrimethylammonium chloride, benzyltriethylammonium chloride ortetramethylammonium chloride or tertiary amines such astriisopropylamine or methylimidazole. Suitable accelerators andcross-linking agents are, for example, basic epoxide group containingcompounds such as triglycidyl isocyanurate, glycolurils, dicyanodiamideor beta-hydroxylamides. These additives may be added individually aspowdered substances. They may also be incorporated as masterbatchesmixed with a proportion of binder or they may be added as a mixture withbinder powder a1).

Furthermore, flame retardant substances may be incorporated. These areconventional, known substances which are contained in fire retardantcoatings. Examples of this type of compound are borates such as sodiumborate, phosphates such as ammonium phosphate or sodium phosphate,aluminium hydroxides or oxides; other suitable compounds are, forexample, heavy metal containing compounds such as tin oxide compounds orperbrominated or perchlorinated compounds such as tetrabromophenol.Preferably, however, flame retardant substances which do not containheavy metals or halogens are used. These flame retardant substances arepresent as powders. They may be incorporated via a separate masterbatchor they may be added via binder powder a1) or a2) each as a homogeneousmixture with the powder component.

Pigments may also be incorporated in binder mixture a). In general,however, preferably no additional pigments are introduced, only thefibrous fillers in the fibre matting being used or the pigmentscontained in powder coatings a2).

The present invention also provides moulded articles which can beproduced by moulding and partly or completely hardening the mixture offibres and binder described above. If the mixtures of fibres and binderare only partly hardened, so-called prepregs are obtained which can thenbe fully cured by placing them in their final mould and heating in afurther processing step. If the mixtures are completely cured, then theyare moulded into the corresponding shape in a manner known per se andcured at cross-linking temperatures suitable for the binder mixture.

The prepregs formed prior to curing or the finished moulded articlescontain in general 55 to 80 wt. % of fibres and 20 to 45 wt. % of bindermixture.

In a preferred embodiment, the binder mixture consists of 45 to 70 wt. %of phenol resins and 30 to 55 wt. % of powder coating binder. Theadditives and auxiliary agents described above may be contained in anamount of up to 20 wt. %, preferably up to 15 wt. %, wherein the sum ofthe individual components is 100 wt. %. Any powder coating waste may beused. Only one type of powder coating or a mixture of several types maybe used, preferably, however, a mixture of polyester and epoxide resinsis used. Furthermore, the preferred ratio of polyester powder to epoxidepowder is 0.2:1 to 7:1, preferably 0.8:1 to 3:1. When selecting thepowder coating waste, however, care should be taken that these possessan adequate number of reactive groups.

To produce moulded articles according to the invention, the bindermixtures are homogenised and applied to the fibre matting, optionallytogether with additives. This takes place using known methods. Thebinder mixture is distributed uniformly on the fibre matting and aheating step is then optionally performed. This softens the binderparticles at the surface and bonds them firmly to the fibre matting.This produces so-called prepregs which are storage-stable, stillmouldable strips of fabric. In this case, care must be taken thatcomplete cross-linking does not occur and that the binder can still befurther moulded when heated and can also flow and be cross-linked.

Binder mixture a), the prepregs and also the cured moulded articles havea reduced proportion of free phenols or formaldehyde. Thus, risks due tothese health-hazardous substances are reduced. The moulded articlesaccording to the invention can be produced from the prepregs obtained inthis way. This takes place using known methods such as thermoformingand/or backing, finally finishing the prepregs. After the prepregs havebeen placed in an appropriate mould, they are cross-linked by applyingpressure and heat. Cross-linking takes place at temperatures of 140° to200° C. The time taken may be between 10 and 500 seconds, preferablyless than 120 seconds. These factors depend on the phenol resin a1)used. The binder powder melts and flows, whereupon the fibres become atleast partially embedded and chemical cross-linking of the resin takesplace. A cured thermoset material is produced. Depending on the amountof material used and on the compression pressure applied, the mouldedarticles may contain a proportion of hollow spaces. The density of themoulded articles may be between 50 and 1000 kg/m³. This depends on theamount and type of fibres and binder. The moulded articles produced havevarious advantages such as good thermal insulation, dimensionalstability up to 130° C., good sound insulation and good flexuralstrength, they are physiologically acceptable and moisture controllingand they are readily further processed.

These moulded articles can also be coated or they can act as supportsfor other structural components. This takes place, for example, byapplying a film to the surface of the moulded article at the same timeas the moulded article is being cross-linked and moulded. This is bondedfirmly to the surface due to a chemical reaction. Furthermore, it ispossible to achieve a special coating for the surface by subsequentlybacking and laminating films. Processes for backing moulded articles arewidely used in industry. They may be performed using the prior art.

Furthermore it is possible to flock spray the surface of the mouldedarticle. In this case, short fibres are applied essentially at rightangles to the surface by means of adhesives which then results in adense, soft surface.

Processes for flock spraying are also known. The moulded articlesproduced from the materials according to the invention may optionally belacquered. For this, any known coating agent known in the industry maybe used. Smooth glossy surfaces are produced after heating.

The moulded articles coated in this way have an attractive anddecorative appearance. Depending on the method chosen, smooth, soft,grained or even chemically resistant coated surfaces may be obtained.The additional use of flame retarding additives can also produce mouldedarticles which are resistant to fire.

The moulded articles obtained in this way may be used in a variety ofindustrial areas. In particular, they may be used in the automobileindustry e.g. as internal panels for automobile interiors or as soundand heat insulation. Furthermore, the binder mixtures may be used asresins in linings for clutches. These resins may also be used toconstruct moulds in the foundry industry. The moulded articles producedare distinguished by a high degree of stability and may be moulded inmany different ways. They may be used in different applications byadding different additives or by coating the surface.

EXAMPLE 1

A mixture of 48 g of a commercially available powdered phenol resin(novolak with hexamethylenetetramine) with an average particle size of35 μm and a cross-linking temperature of 150° C. and 3.4 g of apigmented powder coating based on commercially available epoxide resinpowder, and 10.2 g of a pigmented powder coating based on polyesterresins, wherein the powder coatings each have a pigment content of 13%,is homogenised in a commercial mixing unit.

(polyester:epoxide=3:1, 20% powder coating content)

The mixture can be stored for a long time without further loss inreactivity.

EXAMPLE 2

To 70 g of a phenol resin analogous to the one in example 1 is added apreviously homogenised mixture of 15.8 g of an epoxide resin powdercoating and 14.2 g of a polyester powder coating, both beingunpigmented.

(polyester:epoxide=0.9:1, 30% powder coating content)

To this mixture are added 20 g of a flame retardant based on ammoniumphosphate, melamine borate and aluminium hydroxide and the mixture ishomogenised in a conventional mixing unit. Slight heating up to 40° C.may possibly occur due to the mixing energy. In this case, however, nocaking of the various powder coatings should take place.

EXAMPLE 3

To 60 g of a phenol resin according to example 1 are added 21 g of anepoxide resin coating powder pigmented with 10% of barium sulphate andthe mixture is homogenised. Afterwards, 30.1 g of a non-pigmentedpolyester powder coating is added, as well as 0.4 g oftetrabutylammonium bromide, and the entire mixture is then thoroughlyhomogenised.

(polyester:epoxide=1.6:1, 45% powder coating content)

The mixture is storage-stable over a long period.

The polyester powders or epoxide powders used are filter dusts from theproduction of powder coatings. These are homogenised and then an averagesample of these constituents are used in the examples.

Prepregs are produced from the powders in examples 1 to 3 using afibrous matting which contains more than 80%. cotton fibres, prepared inas known way. To do this, the fibre mats are homogeneously mixed withthe binder powder by mechanical motion and passed through a hot channel(ca. 2-3 min,. 80°-100° C.). Storage-stable prepregs are obtained inwhich resin and fibre have been bonded together.

The prepregs can be produced differently, depending on the size andresin/fibre content. The crude density, depending on the ultimateapplication, is between 25 and 75 kg/m³.

Moulded articles are produced from these prepregs. Here, the prepregsare cut into sections, placed in a press in the desired mould and curedthere for 100 seconds to 110 seconds at temperatures between 140° C. and160° C. After curing, thermoset products which are dimensionally stablein the warm are obtained. The density can be affected by the amount ofprepregs or by the pressure applied. The resulting cross-linked mouldedarticles may be flock sprayed in any known way or they may be backedwith films.

The moulded articles obtained in this way have an optically homogeneoussurface, they are dimensionally stable and have only a small amount offree phenol or formaldehyde.

I claim:
 1. A mixture for producing moulded articles from fibre matscontaining:a) 20 to 45 wt. % of a powdered binder mixture, comprisinga1)30 to 90% wt. % of phenol resin and a2) 70 to 10 wt. % of powder coatingwaste, and b) 80 to 55 wt. % of organic and/or inorganic fibres,whereinthe component a2) consists of powder coating waste which is not yetcross-linked, based on at least one member selected from the groupconsisting of epoxide, polyester, polyurethane and acrylate resinscontaining reactive groups.
 2. A mixture according to claim 1,characterised in that it contains further additives and auxiliaryagents.
 3. A mixture according to claim 1, characterised in that epoxideresin and polyester resin in a ratio of 1:0.2 to 1:7 are used as thepowder coating waste.
 4. A mixture according to claim 1, characterisedin that at least one flame retardant is added as an additive.
 5. Mouldedarticles obtained by moulding and partially or completely hardening amixture according to claim
 1. 6. A method of using powder coating wastewhich is not yet cross-linked, said waste being based on at least onemember selected from the group consisting of epoxide, polyester,polyurethane and acrylate resins containing reactive groups comprisingmoulding articles from fibre mats using a mixture, as follows:a) 20 to45 wt. % of a powdered binder mixture, comprisinga1) 30 to 90% wt. % ofphenol resin and a2) 70 to 10 wt. % of powder coating waste, and b) 80to 55 wt. % of organic and/or inorganic fibres.
 7. A method of usingpowder coating waste which is not yet cross-linked, said waste beingbased on at least one member selected from the group consisting ofepoxide, polyester, polyurethane and/of acrylate resins, containingreactive groups,, comprising bonding fibre mats using a mixture, asfollows:a) 20 to 45 wt. % of a powdered binder mixture, comprisinga1) 30to 90% wt. % of phenol resin and a2) 70 to 10 wt. % of powder coatingwaste, and b) 80 to 55 wt. % of organic and/or inorganic fibres.
 8. Amixture according to claim 2, characterized in that epoxide resin andpolyester resin in a ratio to 1:0.2 to 1:7 are used as the powdercoating waste.
 9. A mixture according to claim 2, characterized in thatat least one flame retardant is added as an additive.
 10. A mixtureaccording to claim 3, characterized in that at least one flame retardantis added as an additive.
 11. Moulded articles obtained by moulding andpartially or completely hardening a mixture according to claim
 2. 12.Moulded articles obtained by moulding and partially or completelyhardening a mixture according to claim
 3. 13. Moulded articles obtainedby moulding and partially or completely hardening a mixture according toclaim 4.